• Journal of the Korean Ceramic Society
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• v.30 no.10
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• pp.811-818
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• 1993

Al2O3/ZrO2-Spinel composites were prepared by infiltrating magnesium sulfate solution into the porous preform made from Al2O3-20wt% ZrO2 composite powders derived through an emulsion route. The microstructure and composition of the modified composites could be controlled by manipulating the presingtering temperature of the preform, infiltration time, and so on. It was found that spinel phases were concentrated near the surface than in the interior of the Al2O3/ZrO2-Spinel composites infiltrated for 6hrs, while spinel phases were uniformly distributed in the comosites infiltrated for 2 days. The relative density and fracture toughness of the composite infiltrated for 6 hrs were 98.6% and 7.2MN/m3/2, respectively.

• Journal of Ecology and Environment
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• v.36 no.4
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• pp.267-271
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• 2013

To examine the density effect and food concentration in the competitive output of two Bosmina species, the population growths of Bosmina fatalis were investigated by manipulating the density of B. longirostris and the concentration of algae. The B. fatalis density did not increase in conditions with abundant B. longirostris regardless of the food concentrations. The B. fatalis increased only at low densities of B. longirostris with high food concentrations. Based on the current results, a possible mechanism underlying the seasonal shift from B. longirostris to B. fatalis in Japanese eutrophic lakes will be explored below.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.42-45
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• 1998

In this paper, a fuzzy control technique using adjustable scale factors and Lyapunov Function for the precise position control of DC servo system is introduced. The suitable scale factors were selected and the stable control input using the stability theory of Lyapunov function cam be applied. Therefore, the controlled system have the robustness against disturbances and can be stabilized because of reinforced adaptivity. This proposed fuzzy controller is implemented on a 80586 micro-computer which have of fuzzy inference routine part, manipulating part of scale factors and DT-2801 data aquisition board.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.603-607
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• 2002

Recently, the need leer transporting and manipulating minute amount of fluids in microscale channels (so-called micro-fluidics) has been increasing, especially in biotechnology and biochemical processing. This work demonstrates that the mechano-chemical process which consists of mechanical abrasive action combined with chemical process can be used to fabricate micro-fluidic channels more rapidly and cost effectively than other methods. In this work, capillary filling of fluids in micro-channels was investigated by theoretical approaches and experiments. From the experimental results, it is expected that a complex micro-fluidic system can be fabricated using the micro- fabrication technique and microsystem packaging method described in this work.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.467-475
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• 1998

The Six Degree-of-Freedom manipulators are generally operated by linear actuators which are hydraulic cylinder, pneumatic cylinder, ball-screw. But these actuators are not adequate to have a wide work-space, and furthermore some of them have a self-locking property. Therfore, we have designed a new manipulator which fully overcomes these demerits. The new manipulating system consists of 6 DC-motors to generate operation forces and 6 position transducers to feedback displacement signals. This paper presents an overview of the design and characteristics of 6 Degree-of-Freedom force feedback manipulators for vitual reality implementation. we can operate Six Degree-of-Freedom manipulator with six motors and six potentiometers.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2016-2025
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• 1994

A hierarchical planning strategy for dextrous manipulation of multifingered hands with soft finger contact model is proposed. Dextrous manipulation planning can be divided into a high-level stage which specifies the position/orientation trajectories of the fingertips on the object and a low-level stage which determines the contact forces and joint trajectories for the fingers. In the low-level stage, various nonlinear optimization problems are formulated according to the contact modes and integrated into a manipulation planning algorithm to find contact forces and joint velocities at each time step. Montana's contact equations are used for the high-level planning. Quasi-static simulation results are presented and illustrated by employing a three-fingered hand manipulating a sphere to demonstrate the validity of the proposed low-level planning strategy.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.106-113
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• 1996

This paper presents a modeling of undersea robot manipulators and a control scheme appropriate for manipulating the manipulators working under the unstrcuctured sea water environment. Under the sea, the added mass and added moment of inertia, buoyancy, and drag forces should be considered in modeling the dynamics of the robot manipulators. Due to the complexity of them, the desired dynamics of manipulators can not be accomplished by the conventional control schemes. Hence, a sliding mode control is applied to control the modeling error.

• Journal of the Ergonomics Society of Korea
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• v.16 no.3
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• pp.11-21
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• 1997

The purpose of this study is to obtain 3-dimensional isocomfort workspace using the robot kinematics, which is based on perceived discomfort in varying postures for manipulating four types of controls. Fifteen healthy male subjects participated in the experiment where their perceived discomfort in the given postures was measured, in which L32 orthogonal array was adopted. The shoulder flexion and adduction-abduction, elbow flexion, types of controls, and right/left hands were selected as experimental variables. The results showed that the shoulder flexion and adduction-abduction, elbow flexion, and types of controls significantly affected the perceived discomfort at .alpha. =0.01. Depending upon the types of control used, regression equations predicting perceived dis- comfort and three dimensional isocomfort workspace were suggested based on the experiemntal cata. Using the equations, driver's isocomfort workspace in his/her cabin for pushing operation was illustrated, in which the robot kinematics was employed to describe the translational relationships between the upper arm and the lower arm/hand. It was ecpected that isocomfort workspace could be used as a valuable guideline to design workplaces ergonomically.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.4
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• pp.97-101
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• 2002

Recently, the need for transporting and manipulating minute amount of fluids in microscale channels (so-called micro-fluidics) has been increasing, especially in biotechnology and biochemical processing. This work demonstrates that the so-called mechano-chemical process which consists of mechanical abrasive action combined with chemical process can be used to f뮤ricate micro-fluidic channels more rapidly and cost effectively than other methods. In this work, capillary filling of fluids in micro-channels was investigated by theoretical approaches and experiments. From the experimental results, it is expected that a complex micro-fluidic system can be fabricated using the micro-fabrication technique and microsystem packaging method described in this work.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.91-97
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• 2005

Bones are dynamic structures, being supported by muscles, tendons, and ligaments. When some or all the structures are disturbed i.e. in fractures, the alignment of the bone in respect to the rest of the body is deranged. This gives rise to axial as well as rotational deformity in three dimensional planes. The correct alignment and position of the long bones are to be maintained to heal the bone in the best possible anatomical and functional position. The objective of this research is to address the problems in the current practice involving surgeon, assistant, fluoroscopy and crude mechanical means and to see if a robotic solution exists to solve the problems of manipulating and reducing long bone fractures. This paper presents various design aspects of the proposed surgeon-instructed, image-guided and robotic system including the system design specification, robot design and analysis, motion control and implementation, and x-ray image processing and incorporation in CAD environment.